Polymerization reaction vessel



Dec. 11, 1951 .1.l F. NELSON POLYMERIZATION REACTION VESSEL Filed July 15, 1944` T N E V W /4 VI E N Dn O H A Patented Dec. 11, 1951 POLYMERIZATION REACTION VESSELV Joseph F. Nelson, Elizabeth, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application July 15, 1944, Serial No. 545,099

6 Claims. (Cl. 223-285) The present invention pertains to the preparation of polymers from isomonoolefins or mixtures of isomonoolei'lns and diolens by the treatment thereof with Friedel-Crafts type catalysts at low temperatures and in particular to a novel reactor which may be utilized for continuous oper-ation of the foregoing polymerization reaction.

High molecular weight polymers such as polyisobutylene of 15,000-25,000 up to about 300,000 molecular weight (as determined by the Staudinger method) have been prepared by polymerizing isomonoolefins such as isobutylene in contact with a Friedel-Crafts type catalyst at temperatures below -10 C. and preferably below 40 C. Products which are vulcanizable or curable with sulfur are obtained if a minor proportion of a dolen is added to a major proportion of an isomonoolefln and the resultant mixture is polymerized at temperatures below 10 C. and preferably at or about -100 C. by the application thereto ofa solution of a Friedel-Crafts type catalyst ina low-freezing, non-complex forming solvent such as a lower alkyl halide, carbon disulfide or the like. These polymerizations have been carried out batchwise and continuously and with lique-V fled ethylene added to the reaction mixture` as a diluent-refrigerant or in the presence of substantial amounts of alkyl halides and the like as diluents in apparatus provided with means for absorbing the exothermic heat of reaction. By and large the latter has been found to be the preferred method of conducting the polymerization since it not only lends itself well to continuous operation but is capable of better control with the formation of polymers of improved physical characteristics in greater yields. A reactor of this type is disclosed and claimed in application Serial No. 448,575, filed June 26, 1942, nowabandoned, by John H. Bannon. In this reactor a draft tube provided with an agitator is arranged centrally of the reactor and a plurality of return tubes are arranged between headers arranged around the central draft tube with means for circulating a Asuitable refrigerant, desirably ethylene through the space between the headers and around the central draft tube aswell as the return tubes. This type of reactor has been used extensively for this type of reaction since a maximum amount of heat transfer surface can be obtained in this way in a reactor of a given height and volume. A serious problem encountered with this reactor is that of accumulation of polymer on the upper entrance tube sheet and plugging of the return tubes, especially at their entrance ends. The exact cause of this trouble has neverl been deter-f 2` mined but it has been general and persistent un-v der widely varying conditions of operation. v

Itis the object of this invention to provide the art with a novelv type of reactor. A

.It is a further object of this invention to provide the art with a polymerization reactor of the indirect heatexchange type which is relatively free of tendencies to plug. f y i f It is also the object of this invention to provide the art with areactor of the heat exchange type in which the reaction mixture is recirculated in highly agitated and turbulent iiow.

Itis a further object of this invention to provide the art with polymerization reactors having an improved heat transfer coefficient.

.These and other objects will appear more clearly from the detailed description and claims which follow.

It has now been found that a polymerization reactor which is practically free from tendencies to plug and which possesses a high heat transfer coeiiicient is obtained if the reactor is constructed with a central draft tube provided with` an impellerand a return tube made in the form of an annular'passageway completely surrounding the drafttube and provision is made for maintaining a refrigerant in contact with each of the wall surfaces with which the reaction mixture comes into contact. Under the impetus of the impeller or agitator the reaction mixture moves upwardly through the central draft tube as a swirling, turbulent stream and since there are no obstructions in the return passageway other than a few crossovermembers for supplying refrigerant to `the space between the centralrdraft tube and the inner wall of the annular return passageway the return ow through thev annular passageway is substantially as swirling and turbulent as that in the central draft tube. The reaction mixture follows a vgenerally helical course upwardly in the central draft tubeand also downwardly in the return annular channel, thereby substantially increasing the amount of contact of the reaction mixture with the cooling surfaces, this flow contributing to the high heat transfer coeiicient of the reactor in accordance with the present invention. While the flow is indicated as being upwardly in the central draft tube and downwardly in the return annulus-it will be understood that the direction of ow could just as well be downf wardly in thercentral draft tube and upwardly in the return annulus.

Referenceis made to the accompanying drawf ing .which illustrates the reactor of the present invention. Y

Figure 1 is a vertical cross-section of the polymerization reactor, and

Figure 2 is a horizontal cross-section of the reactor along the line A-A of Figure 1.

Referring to the drawings, the reactor comprises an Outeriielllglnber l .Wtl .Wlh a?? arranged acentral drfttube ,2'and an anniilar return passageway 3 formed by inner cylindrical wall 4 and an outer cylindrical wall 5. In order to remove the exothermic heat of reaction a refrlgerant is supplied to an outer cooling jaeketnll comprising the space between the outer shell member l and the cylindrical well s and also .to

an inner cooling jacket 22 1criirisin the space between the inner Wall member 4 and the central draft tube 2. The refrigerantis supplicdtqthe recator through inlet 6 and is withdrawnL genv-v l erally in vaporized form, through the 'litlet L A plurality of Crossovers 8 are arranged to carry tile refrigerant the 'annular passageway into the innerl cooling jacket 22. rn' order to reduce the number of 'obstructions in the circulating reaction mixture "stream, th' crossover niem- 8 are prefer'ablyinade lof 'Suiilcient size and strengthens are attached Ato well members '4 and 'sl'li'ciently securely as by welding t support theuentire wall 4 and central draft tube asi Y `A vro'peller' -a'gitator `9 of any desired type ii'ileft l 'is also provided for the supply 'ef catalyst s: lution zone of relatively high turbulence in the reactor. 'Outletports I4k ar'e arranged 'at 'the upper portion of 'the reactor 'tofperrrl'it withdrawal ofu reaction 'slurry from the reactor. Valves is; preferably ef 'the biu'ii'gier 'jer fplstoii type, are are ranged trie Voutlet ports "in order-te "control the outflowfrom theb reacfr. Piston type valves -are preferred since they are "self-cleaning and lie iiu'svh `with the `'inside wall of tl'ie Vreaicto'r when ellisse..

l `rlfhe of lthe reactor is closed'rb'y means "of e head l It which rests 'upon lags "n en the reactor shell erle lese'eii'rea ifi plate durl'rigepeifetie'n by bolts or any suitable' clamping arrangement which permits ready removal 'of the "liead 'for in"- spection or :cleaning of th'e reactor. llifting'lugs I 'lna're provided on the head I'S for 'convenience in removing 'the head. l. Y

The 'nietli'odf operation of. the reactor Tin eerdaiice with the vpresent 'invention is substantially as follows: The lr'eacttir is 'filled with l'reaction mixture, :preferably lprecooled| comprising a current such as methyl chloride and isoolenn suchfa's isobutylene 'or 'mixtures of isobutyle'ne and adioleiln s`ucli `as butadiene. YA refrigerant, prefeablyliquid ethylene, vi's introduced into the' otei'dcoolirig jacket 2| and through Crossovers 8 into the innercoolin'g 'jacket `22. The pressure on the ethyler'ie'i's 'about atmospheric, at which pres- Sll tbiling point ofethylene isabt -150'F. The agitator 9 is placed in operation 'causing the reaction 'mixture to vrise in the 'central 'draft tube and return 'through the :annular =passageway. Assuming counterclockwise rotation of `.the :agb tator the reaction stream rising in the central draft tube is given a rapid counterclockwise rotary or swirling movement which continues not only in the space at the top of the draft tube but in the return passageway 3 causing the reaction liquid to circle the inner jacket in passing from the central draft tube overiiow I9 to the draft tib' 1iiilt zone 2l.

When the reaction mixture has been cooled to the desired reaction temperature, a dilute sollition of a Friedel-Crafts type catalyst in a low freezing non-.complex forming solvent such as nl'thyl-, 'thyl- 6r propyl chloride or carbon disuliide preco'oled to about reaction temperature isuintro'tluced into the reaction mixture through catalyst inlet 13;' The feed of fresh reaction mixture, desirably preooled to about reaction temperature` l,and catalyst solution, are correlated in such 'a way as to give the desired degree of c'onversion in the reactor. .Reaction mixture comprising a .slurry of 1solidpolyxner particles in a mixture of unreacted oleiinic materials and diluent continuously overflows the reactor through outlet port I4 and is passed 'either to suitable flashing equipment wherein the low boiling materials are vaporize'd, as by dropping the slurry into a heated flashing liquid, or to `a filtering or screening fdevice whichvwill separate the polymer particles from the cold reaction liquid which is th'en suitable for immediate recycling to the reactor.

The present invention is applicable to the preparation of any solid. high molecular weight, low temperature polymerizates from isoolefinic hydrocarbons or from mixtures of 'lsooleiinic :hydrocarbons with a diolefinic compound capable .of copolymerlzing with isooiefinic materials at low temperatures in the presence of Friedel-Crafts type catalysts. The preferred isoolen is isobutylene but other isoolens containing up to about 8 c'arbon'atoms per molecule may be used. The copolymerizable 'dioleflnic materials include butadienes and substituted butadien'es, especially i'so'prene, piperylene a'nd ydimethyl butadiene. Other polyol'eiinic materials containing up to -12 or I4 carbon atoms per 'molecule vsuch -as myrce'n'e and ycertain non-conjugated diolens, 4such as dimethylallene Yancl the like, `are also useful. The ratio of i'soolen to diolen in the liquid is from about '50 to 99 Weight p'er centof isooletln to'about 50 to 1 weightfper cent of 'dioleiin when the latter vils a C4 diolefin. With C5 Vand higher dlolefins, the arnourlt of diolefln is less than-10 weight pe'r `oentand'preferably less than 5 weight per cent.

u The catalyst used may be Vboron fluoride, either gaseous or in solution, tor it'may be Va solution of a conventional Friedel-Crafts type catalyst such as aluminum chloride or the other materials listed on page '375 'of the article on Friedel- Crafts Synthesis `by N. O. Calloway, published in Chemical Reviews,.vol\mie 17, No. 3 in 1935. For catalyst solvent, there may be us'ed 4a monoor polyhalogenatedalkyl Isolvent containing less than5 carbon atomsper molecule, `carbon disul'- fide or the like. Dilu'e'liis Ithat may rbe used in the process 'include the alkyl 'halides containing less Ythan 5 carbon atoms, lpreferably methyl chloride 4as well as hydrocarbons containing -less than yabout 5 carbon atoms such as methane, ethane or ethylene.

There are certain conditions under which the polymer slurries are A lnstable and such conditions should be avoided `in order to achieve the I best results. Agglomeration of ithe polymer in the polymer slurry is favored by higher temperauw-,suer

atur'es, lower molecular weight-'of the polymer,

the use of diluents which tend to -be'mutually soluble with the polymer under the operating conditions, aswell as the use 0f larger proportions of hydrocarbon reagents which are alsomutuallysoluble withl theV polymer as l welll a s"`ex cessive degree of dispersion of thecatalyst;

Stable slurries ofv polybutenes can be produced at -90 C. with methyl chloride is`obutylene feeds by maintaining a volumeratio of methyl chloe' ride to isobutylene over about 0.7:"1 in the reac tion mixture, with good agitation throughout the slurry (Reynolds numbers over about 5,0006,000 and preferably over 10,000). At higher'temperatures, higher diluent ratios arev required up to temperatures of about -50 C. which is-the approximate limit for high molecular weight polymer slurry. This temperature effect on molecuf lar weight has been described by Thomas, Sparks, Frolich, Otto and Mueller-Cunradi in the Journal of the American Chemical Society, vol. 62, page 276 (1940). As is also indicated in that article, impurities in the reaction mixture tend to lower the molecular weight and the lower the molecular weight of the polymer the higher the diluent ratio required to form a satisfactory slurry.

The same general principles apply to the production of low temperature isoolen-dioleiln copolymerizate slurries. The molecular weights of these polymers, as determined by the Staudinger method, are considerably lower than those of y C., diluent ratios above 1:1 and preferably overy 2:1 should obtain in the reaction zone. In the manufacture of these copolymers the reaction temperature should not exceed about C. When using aluminum chloride-methyl chloride catalyst solutions, the concentration of aluminum chloride may be up to about l gram per 100 cc. Low temperature isoolefn-diolen copolymers of normal molecular weight for use as rubber substitutes, i. e., having a Staudinger molecular weight of about 30,000 and above can be maintained as a slurry provided that the per cent hydrocarbon or other mutual solvent is not too high. Thus when the reaction liquid contains 60-90 weight per cent of methyl chloride, the slurries containing polymer averaging over roughly 30,000 molecular weight are quite stable, but if the percentage of methyl chloride isireduced to about 30% the slurry becomes unstable and the polymer particles tend to agglomerate. With increasing diolefin content of the isoolefindiolen feed, the molecular weight of the result` ant copolymer is lowered and the temperature necessary for the maintenance of a stable slurry is lowered. Increasing diluent ratio will also compensate, to a limited extent, for lower molecular weight of polymer, thereby permitting slurry formation. f The foregoing description contains a limited number of embodiments of the present invention but it will be understood that numerous variations are possible without departing from the purview of this invention as defined in the following claims.

What I claim and desire to secure by Letters Patent is:

1; An improved reactor vessel comprising a cylindrical shell, a cylindrical reactionV conduit member concentrically of said shell, and having upper and lower ends terminating in vertically spaced relation tothe top and bottom of said shell and with vthe side walls in radially spacedV relation, an annular reaction conduit member. concentric with said cylindrical member and the f. shell, disposed'between said cylindrical member fluid tight union with the upper and lower ends of said cylindrical member and with `the shell respectively, and forming therewith concentricY annular chambers between the wall portions of saidfannular conduit and the walls of said shell and cylindrical conduit member respectively, seprials through said shell and the conduit members, and conduit means communicating with said annular chambers to circulate a heat exchange medium therethrough.

2.' An improved reactor vessel as described in claim 1 in which said conduit means for circulating a heat exchange medium through said annular chamber comprises an inlet and outlet for said medium, each opening through the shell, and a plurality of radially disposed conduit elements communicating between chambers.

3. An improved reactor vessel as described in claim 2 in which the radial conduit elements eX- tend between chambers through said annular conduit in vertically spaced relation to each other and to the upper and lower ends thereof.

4. An improved reactor vessel comprising a cylindrical shell, a cylindrical reaction conduit member concentrically of said shell, and having upper and lower ends terminating in vertically spaced relation to the top and bottom of said shell and with the side walls in radially spaced relation, an annular reaction conduit member, concentric with said cylindrical member and the shell, disposed between said cylindrical member and the shell side walls, in radially spaced relation to each other, said annular conduit member including inner and outer wall portions, the upper and lower 'ends of which are divergently flared into fluid tight union with the upper and lower ends of said cylindrical member and with the shell respectively, and forming therewith concentric annular chambers between the wall portions of said annular conduit and the walls of said shell and cylindrical conduit member respectively, means for supporting and fixing the annular and cylindrical conduit member in relation to said shell, separate means for introducing process materials into said shell and for removing a product therefrom, means for circulating said reactant materials through said shell and the conduit members, and conduit means communicating with said annular chambers to circulate a heat exchange medium therethrough.

5. An improved reactor vessel as described in claim 4 in which said means for supporting and xing the annular conduit member for circulating a heat exchange medium through said annular chamber, and comprises an inlet and outlet for said medium, each opening through the shell, and a plurality of radially disposed conduit elements communicating between chambers.

6. An improved reactor vessel comprising a cylindrical shell, a cylindrical upflow reaction conduit member concentrically of said shell, and having upper and lower ends terminating in vertically spaced relation to the top and bottom of said shell and with the side walls in radially spaced 

1. AN IMPROVED REACTOR VESSEL COMPRISING A CYLINDRICAL SHELL, A CYLINDRICAL REACTION CONDUIT MEMBER CONCENTRICALLY OF SAID SHELL, AND HAVING UPPER, AND LOWER ENDS TERMINATING IN VERTICALLY SPACED RELATION TO THE TOP AND BOTTOM OF SAID SHELL AND WITH THE SIDE WALLS IN RADIALLY SPACED RELATION, AN ANNULAR REACTION CONNDUIT MEMBER, CONCENTRIC WITH SAID CYLINDRICAL MEMBER AND THE SHELL, DISPOSED BETWEEN SAID CYLINDRICAL MEMBER AND THE SHELL SIDEWALLS, IN RADIALLY SPACED RELATION TO EACH, THE UPPER AND LOWER END PORTIONS OF SAID ANNULAR MEMBER DIVERGENTLY FLARED INTO FLUID TIGHT UNION WITH THE UPPER AND LOWER ENDS OF SAID CYLINDRICAL MEMBER AND WITH THE SHELL RESPECTIVELY, AND FORMING THEREWITH CONCENTRIC ANNULAR CHAMBERS BETWEEN THE WALL PORTIONS OF SAID ANNULAR CONDUIT AND THE WALLS OF SAID SHELL AND CYLINDRICAL CONDUIT MEMBER RESPECTIVELY SEPARATE MEANS FOR INTRODUCING PROCESS MATERIALS INTO SAID SHELL AND FOR REMOVING A PRODUCT THEREFROM, MEANS FOR CIRCULATING SAID REACTANT MATERIALS THROUGH SAID SHELL AND THE CONDUIT MEMBERS, AND CONDUIT MEANS COMMUNICATING WITH SAID ANNULAR CHAMBERS TO CIRCULATE A HEAT EXCHANGE MEDIUM THERETHROUGH. 